Active Surveillance vs Adjuvant Chemoradiotherapy for Locally Resected Intermediate-Risk T1 Rectal Cancer (T-REX)

Active Surveillance vs Adjuvant Chemoradiotherapy for Locally Resected Intermediate-Risk T1 Rectal Cancer: Multicentre Randomised Controlled Trial

The goal of this clinical trial is to learn if close follow-up alone (active surveillance) works as well as radiation combined with chemotherapy (chemoradiotherapy) after removing early rectal cancer in adults. The main questions it aims to answer are:

1. Does active surveillance cause fewer serious adverse events than chemoradiotherapy within 3 years? Serious adverse events include a permanent or temporary ostomy (a surgical opening in the belly to pass stool), major bowel problems, or severe treatment-related complications.
2. Is active surveillance as safe as chemoradiotherapy in preventing cancer from coming back or spreading within 3 years?

Researchers will compare active surveillance to chemoradiotherapy to see if surveillance causes fewer serious adverse events while keeping cancer outcomes comparable.

To join this study, participants must be adults who had an early-stage rectal cancer (T1) removed by an endoscopic procedure, and whose removed tumor showed certain features that raise the risk of cancer cells remaining nearby.

Participants will be randomly placed in one of two groups:

1. Active surveillance group: Participants will have regular checkups, blood tests, flexible camera exams of the bowel (rectoscopy), scans of the pelvis and abdomen, and colonoscopy on a set schedule for 5 years. If cancer comes back, doctors will propose further treatment options.
2. Chemoradiotherapy group: Participants will receive radiation to the pelvis along with a chemotherapy pill (capecitabine) or an intravenous (IV) chemotherapy drug (5-FU) for about 5 weeks. After treatment, they will have regular checkups and scans for 5 years.

Study Overview

• Status: Recruiting
• Conditions: Rectal Cancer
• Intervention / Treatment: Other: Active surveillance; Radiation: Adjuvant chemoradiotherapy

Detailed Description

The current standard treatment for T1 rectal cancer (T1N0M0) is local excision by endoscopic submucosal dissection (ESD) or intermuscular dissection (IMD) performed endoscopically or via transanal minimally invasive surgery (TAMIS). More than half of the patients treated with ESD or IMD require secondary treatment due to unfavourable histopathological features in the resected specimen. Lesions can be classified as intermediate-risk if the specimen presents at least one of the following features: poor differentiation (grade 3), lymphovascular invasion, high-grade tumour budding (grade 2-3), or deep submucosal invasion (sm2-sm3).

Secondary treatment can be performed either by total mesorectal excision (TME) or adjuvant chemoradiotherapy. The latest evidence suggests that chemoradiotherapy may offer a superior risk-benefit ratio compared to completion TME. Still, chemoradiotherapy remains associated with a substantial risk of major low anterior resection syndrome (LARS); the risk is reduced but still reported at approximately 25-33%. Given a 15-20% risk of lymph node involvement in the intermediate-risk group, chemoradiotherapy might be overtreatment for the majority of these patients. Active surveillance can reduce treatment-related morbidity, but it is associated with higher local recurrence rates. Available cohort data suggest that most recurrences are detected early during structured surveillance and are salvageable with curative-intent surgery, resulting in oncological outcomes similar to those achieved with adjuvant chemoradiotherapy. However, no randomised trial has directly compared these two strategies in this population.

• Study Type: Interventional
• Enrollment (Estimated): 480
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Michal Kaminski, Prof.; Phone Number: (22) 546 23 28; Email: michal.kaminski@nio.gov.pl

Study Locations

• France
  • Limoges, France
    • Not yet recruiting
    • University Hospital, Limoges
    • Contact: Jeremie Jacques, Prof.; Phone Number: 05 55 05 87 72; Email: josette.rebours@chu-limoges.fr
    • Principal Investigator: Jeremie Jacques, Prof.
• Poland
  • Gdansk, Poland, 80210
    • Recruiting
    • University Clinical Centre
    • Principal Investigator: Piotr Spychalski, MD, PhD
    • Contact: Piotr Spychalski, MD, PhD; Phone Number: (58) 349 20 00; Email: piotr.spychalski@gumed.edu.pl
    • Sub-Investigator: Jaroslaw Kobiela, Prof.
    • Sub-Investigator: Piotr Wysocki, MD, PhD
    • Sub-Investigator: Katarzyna Polomska
  • Warsaw, Poland
    • Recruiting
    • Institute of Oncology in Warsaw
    • Contact: Michal Kaminski, Prof.; Phone Number: (22) 546 23 28; Email: michal.kaminski@nio.gov.pl
    • Principal Investigator: Michal Kaminski, Prof.
    • Sub-Investigator: Nastazja Pilonis, Prof.

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

1. Pathologically confirmed rectal cancer located extraperitoneally.
2. Complete tumour resection (R0) by means of ESD or IMD (endoscopic or TAMIS).

3. Pathological report indicative of:

   - pT1 with at least 1 of the following features: poor histological differentiation (grade 3), vascular invasion, lymphatic invasion, high tumour budding (grade 2-3), sm2 or sm3 invasion.

4. Endoscopic images or video of the tumour before local excision.
5. Maximum cancer diameter ≤ 30 mm based on the pathological assessment.

6. cN0 stage based on pelvic MRI; lymph nodes smaller than 10 mm will be considered as benign, independent of morphologic features. Staging must be performed within 6 weeks before randomisation.

   - If enlarged lymph nodes are present on MRI performed after ESD/IMD (raising the possibility of reactive inflammatory change), fine needle aspiration (FNA) will be undertaken, and patients with negative FNA cytology will remain eligible.

7. Adequate distant staging (thoracic and abdominal CT) without signs of distant metastasis (cM0).

8. Have undergone a high-quality full colonoscopy:

   • Boston Bowel Preparation Scale score equal or greater than 2 in all colonic segments.
   • Documented caecal intubation.
   • All polyps ≥20 mm in diameter other than the index lesion must be completely removed and assessed pathologically.
9. Expected survival time of more than 12 months from randomisation.
10. At least 18 years old at the time of informed consent.
11. Eastern Cooperative Oncology Group performance status (ECOG PS) 0, 1 or 2.

12. Adequate hematologic function, based upon meeting the following laboratory criteria within 7 days before randomisation:

    • Absolute neutrophil count (ANC) ≥ 1.5 × 10^9/L.
    • Haemoglobin (Hb) ≥ 8.0 g/dL (red blood cell transfusions are allowed to reach the target level).
    • Platelet count ≥ 75 × 10^9/L.

13. Adequate liver function, based upon meeting the following criteria within 7 days before randomisation:

    • Serum albumin ≥ 3.0 g/dL.
    • Total bilirubin (in serum) ≤ 2.0 mg/dL.
    • Aspartate aminotransferase (AST) ≤ 3 × the upper limit of normal (ULN).
    • Alanine aminotransferase (ALT) ≤ 3× ULN.
    • Alkaline phosphatase (ALP) ≤ 3 × ULN.
14. Adequate coagulation defined by International Normalized Ratio (INR) ≤ 2.0 within 7 days before randomisation.

15. Adequate renal function, based upon meeting the following laboratory criteria within 7 days before randomisation:

    • Serum creatinine clearance ≥ 50 mL/min calculated using the Cockcroft-Gault formula.
    • Absence of significant proteinuria. If the subject is found to have dipstick test indicative of proteinuria equal or larger than 2+, or lab urinalysis for protein is greater than or equal to 1 g/L, the subject must demonstrate urine protein < 1 g/24 h to be eligible.
16. Recovery from prior treatment-related toxicities to < Grade 2 severity per CTCAE v6.0, unless the adverse events are clinically nonsignificant and/or stable on supportive therapy.
17. Sexually active fertile subjects and their partners must agree to use medically accepted methods of contraception (e.g., barrier methods, including male condom, female condom, or diaphragm with spermicidal gel) during the study treatment. This does not apply to postmenopausal women (amenorrhoeic for at least 12 consecutive months), women aged above 55, or surgically sterilized patients (men and women).

18. Female participants of childbearing potential must not be lactating or pregnant, with a negative beta-human chorionic gonadotropin (beta-hCG) test (blood or urine) at screening and before the first dose of the study treatment.

    Females of childbearing potential are defined as premenopausal females capable of becoming pregnant (i.e., females who have had any evidence of menses in the past 12 months, except for those who had prior hysterectomy). However, women who have been amenorrhoeic for 12 or more months are still considered to be of childbearing potential if the amenorrhea is possibly due to prior chemotherapy, antioestrogens, ovarian suppression, low body weight, or other reasons.

19. Written informed consent to participate in the study provided before randomisation.
20. Capability of understanding and complying with the protocol requirements.
21. Absence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial.
22. Eligibility for thoracic, abdominal and pelvic CT and MRI.

Exclusion Criteria:

1. Suspicion of distant metastases on computed tomography of the abdomen or thorax or lymph node involvement (lymph nodes >9mm in short axis); In case of isolated enlarged nodes biopsy will be required before exclusion.
2. Mesorectal tumour involvement on pelvic MRI.
3. Synchronous colorectal cancer in screening colonoscopy.
4. Known genetic cancer syndrome, including, but not limited to adenomatous or serrated polyposis syndrome; Lynch or Lynch-like syndrome.
5. Known inflammatory bowel disease.
6. Previously identified allergy or hypersensitivity to 5-FU or capecitabine.
7. Known or suspected dihydropyridine dehydrogenase (DPD) deficiency.
8. Prior receipt of pelvic radiation.
9. Other contraindications to pelvic irradiation.
10. Serious illness other than cancer that would preclude safe participation in the study

11. Uncontrolled and significant condition, including, but not limited to, the following conditions:

    • Heart failure NYHA II or above.
    • Major cardiac arrhythmia.
    • Myocardial infarction within 6 months before randomisation.
    • Unstable angina pectoris.
    • Stroke (including transient ischemic attack, TIA) within 6 months before randomisation.
    • Thromboembolism within 3 months before randomisation.
    • History of hypertensive crisis.
12. Gastrointestinal disorders associated with a high risk of perforation or fistula formation.
13. Gastrointestinal bleeding event within 28 days of randomisation.
14. Major surgery performed within 4 weeks prior to randomisation or scheduled for surgery during the study period. Complete healing from major surgery must have occurred 1 month before randomisation. Complete healing from minor surgery must have occurred at least 7 days before randomisation.
15. Serious non-healing wound or bone fracture.
16. Malabsorption syndrome.
17. Pregnancy or lactation.
18. Mismatch repair deficiency (dMMR) or microsatellite instability-high (MSI-H).

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Active surveillance	Other: Active surveillance; Active surveillance includes physical examination, and carcinoembryonic antigen (CEA) testing every 3 months during years 1-2 and every 6 months during years 3-5. Rectoscopy is performed every 3 months during years 1-2 and every 6 months during years 3-5. Pelvic MRI is performed every 6 months for 5 years. Thoracic and abdominal CT scans are performed annually for 5 years. Colonoscopy is performed at 1 year after local excision and subsequently according to findings. Recurrences are managed according to multidisciplinary team recommendations.
Active Comparator: Adjuvant chemoradiotherapy	Radiation: Adjuvant chemoradiotherapy; Adjuvant long-course pelvic chemoradiotherapy will be initiated within 12 weeks after local excision. Radiotherapy consists of 45 Gy delivered in 25 fractions of 1.8 Gy once daily, 5 days per week, over approximately 5 weeks. Concurrent chemotherapy consists of either oral capecitabine 825 mg/m² twice daily on radiotherapy days or continuous intravenous 5-fluorouracil 225 mg/m²/day throughout radiotherapy. After treatment, follow-up includes history, physical examination, CEA testing, and flexible sigmoidoscopy every 6 months for 5 years; pelvic MRI every 6 months during the first 3 years; annual thoracic and abdominal CT for 5 years; pelvic CT after discontinuation of MRI surveillance; and colonoscopy at 1 year and thereafter according to findings.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Disease-related treatment failure	Time from randomisation to the first occurrence of: Cancer specific death.; Non-salvageable locoregional recurrence.; Distant metastases.	3 years from randomisation
Composite severe treatment-related adverse event	Occurrence of any of the following: Stoma (permanent or temporary).; Major LARS (score ≥30).; CTCAE grade ≥3 toxicity.; Clavien-Dindo ≥3b complications.	3 years from randomisation

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Disease-free survival	Time from randomisation to first event: death (any cause), distant metastases, or locoregional recurrence	3 and 5 years after randomization
Overall Survival	Time from randomization to death from any cause.	3 and 5 years after randomization
Stoma formation rate	Proportion of patients with a colostomy or ileostomy (permanent or temporary) present at assessment. Stoma rates will be evaluated at predefined follow-up intervals.	12 months, 3 years, and 5 years after randomization
Incidence of Major Low Anterior Resection Syndrome (LARS)	Proportion of patients with a LARS Questionnaire score of 30 points or greater, indicating major low anterior resection syndrome.	12 months, 3 years, and 5 years after treatment
Grade 3 or Higher Treatment-Related Toxicity	Incidence of adverse events of grade 3 or higher according to Common Terminology Criteria for Adverse Events (CTCAE) version 6.0 occurring during treatment and follow-up.	From treatment initiation through 12 months after completion of chemoradiotherapy.
Locoregional Recurrence Rate	Proportion of patients with radiologically or histologically confirmed recurrence within the pelvis or mesorectum.	5 years after randomization.
Salvageability of Locoregional Recurrence	Proportion of detected locoregional recurrences amenable to curative-intent salvage therapy.	At the time of recurrence detection, up to 5 years after randomization
Duration of Hospital Stay After Primary Treatment	Total cumulative length of hospitalization following the randomized treatment strategy, measured in calendar days.	From the day of randomization untill 5 years from randomization.
Distant Recurrence Rate	Proportion of patients with radiologically or histologically confirmed distant metastatic disease outside the locoregional area.	3 years and 5 years after randomization.
Health-Related Quality of Life (EORTC QLQ-C30)	Health-related quality of life assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire - Core 30 (EORTC QLQ-C30).	Baseline, 12 months, 3 years, and 5 years after randomization
Healthcare Resource Utilization Costs per Patient	Direct healthcare resource utilization costs including treatment, procedures, imaging, hospitalization, surveillance, and management of recurrence and complications measured as a total per patient in euro (€).	Up to 5 years after randomization.
Cost-Effectiveness	Incremental cost-effectiveness expressed as cost per quality-adjusted life-year (QALY) gained and cost per disease-free survival year gained.	3 years and 5 years after randomization
Ostomy-Free Survival	Time from randomization to permanent ostomy formation or death, with estimation of the proportion of patients alive without a permanent ostomy.	3 years and 5 years after randomization.
Health-Related Quality of Life (EORTC QLQ-CR29)	Health-related quality of life assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire - Colorectal Cancer Module (EORTC QLQ-CR29).	Baseline, 12 months, 3 years, and 5 years after randomization.

Collaborators and Investigators

• Sponsor: Medical University of Gdansk
• Collaborators: Vestre Viken Hospital Trust; University of Oslo; Karolinska Institutet; University of Roma La Sapienza; Hospital Clinic of Barcelona; Helse Stavanger HF; Haukeland University Hospital; Sorlandet Hospital HF; St. Olavs Hospital; University Hospital, Ghent; University Hospital, Akershus; Universitätsklinikum Hamburg-Eppendorf; Maria Sklodowska-Curie National Research Institute of Oncology; Leuven University Medical Center; Centre Hospitalier Universitaire Dupuytren de Limoges (CHUL); Northern Norway Regional Health Trust

Publications and helpful links

General Publications

• Emmertsen KJ, Laurberg S. Low anterior resection syndrome score: development and validation of a symptom-based scoring system for bowel dysfunction after low anterior resection for rectal cancer. Ann Surg. 2012 May;255(5):922-8. doi: 10.1097/SLA.0b013e31824f1c21.
• van Oostendorp SE, Smits LJH, Vroom Y, Detering R, Heymans MW, Moons LMG, Tanis PJ, de Graaf EJR, Cunningham C, Denost Q, Kusters M, Tuynman JB. Local recurrence after local excision of early rectal cancer: a meta-analysis of completion TME, adjuvant (chemo)radiation, or no additional treatment. Br J Surg. 2020 Dec;107(13):1719-1730. doi: 10.1002/bjs.12040. Epub 2020 Sep 16.
• Ouchi A, Komori K, Masahiro T, Toriyama K, Kajiwara Y, Oka S, Fukunaga Y, Hotta K, Ikematsu H, Tsukamoto S, Nagata S, Yamada K, Konno M, Ishihara S, Saitoh Y, Matsuda K, Togashi K, Ishiguro M, Kuwai T, Okuyama T, Ohuchi A, Ohnuma S, Sakamoto K, Sugai T, Katsumata K, Matsushita HO, Nakai K, Uraoka T, Akimoto N, Kobayashi H, Ajioka Y, Sugihara K, Ueno H; Study Group for the JSCCR-T study. How Does Omitting Additional Surgery After Local Excision Affect the Prognostic Outcome of Patients With High-risk T1 Colorectal Cancer? Ann Surg. 2024 Feb 1;279(2):290-296. doi: 10.1097/SLA.0000000000006092. Epub 2023 Sep 5.
• Corre F, Albouys J, Tran VT, Lepilliez V, Ratone JP, Coron E, Lambin T, Rahmi G, Karsenti D, Canard JM, Chabrun E, Camus M, Wallenhorst T, Chevaux JB, Schaefer M, Gerard R, Rouquette A, Terris B, Coriat R, Jacques J, Barret M, Pioche M, Chaussade S, Cappelle E. Impact of surgery after endoscopically resected high-risk T1 colorectal cancer: results of an emulated target trial. Gastrointest Endosc. 2024 Mar;99(3):408-416.e2. doi: 10.1016/j.gie.2023.09.027. Epub 2023 Oct 2.
• Moolenaar LR, van Geffen EGM, Hazen SJA, Sluckin TC, Beets GL, Leijtens JWA, Talsma AK, de Wilt JHW, Tanis PJ, Kusters M, Hompes R, Tuynman JB; Dutch Snapshot Research Group; Collaborators Snapshot Registry. Salvageable locoregional recurrence and stoma rate after local excision of pT1-2 rectal cancer - A nationwide cross-sectional cohort study. Eur J Surg Oncol. 2025 Jun;51(6):109623. doi: 10.1016/j.ejso.2025.109623. Epub 2025 Jan 23.
• Serra-Aracil X, Pericay C, Cidoncha A, Badia-Closa J, Golda T, Kreisler E, Hernandez P, Targarona E, Borda-Arrizabalaga N, Reina A, Delgado S, Espin-Bassany E, Caro-Tarrago A, Gallego-Plazas J, Pascual M, Alvarez-Laso C, Guadalajara-Labajo H, Otero A, Biondo S; TAUTEM Collaborative Group. Chemoradiotherapy and Local Excision vs Total Mesorectal Excision in T2-T3ab, N0, M0 Rectal Cancer: The TAUTEM Randomized Clinical Trial. JAMA Surg. 2025 Jul 1;160(7):783-793. doi: 10.1001/jamasurg.2025.1398.
• van der Schee L, Albers SC, Didden P, Lacle MM, Farina Sarasqueta A, Richir MC, Intven MPW, Tuynman JB, Hompes R, Dekker E, Vleggaar FP, Bastiaansen BAJ, Moons LMG. Results of endoscopic intermuscular dissection for deep submucosal invasive rectal cancer: a three-year follow-up study. Gut. 2025 Nov 10;74(12):1995-2003. doi: 10.1136/gutjnl-2024-334612.
• Moolenaar LR, Ali M, Aufenacker TJ, Beets GL, Bosker RJI, Buffart TE, Burger JW, Dekker E, Denost Q, Doornebosch PG, Duijvendijk PV, Fabry HFJ, Geijsen ED, Gerhards MF, van Grevenstein WMU, Grotenhuis BA, Hoff C, Leijtens JWA, Peeters KCMJ, Pronk A, van der Schelling GP, Sietses C, Smits AB, Toorenvliet BR, van de Ven AWH, Verdaasdonk EGG, Vuylsteke RJCLM, van Westreenen HL, de Wilt JHW, Zimmerman DDE, Lange MM, van Grieken NCT, Bastiaansen BAJ, Hompes R, Marijnen CA, Dijkgraaf MGW, Moons LMG, Tanis PJ, Cunningham C, Tuynman JB; TESAR Study Group. Adjuvant chemoradiotherapy versus completion total mesorectal excision after local excision for early rectal cancer (TESAR): a multicentre, randomised, controlled, phase 3, non-inferiority trial. Lancet Gastroenterol Hepatol. 2026 May 27:S2468-1253(26)00109-3. doi: 10.1016/S2468-1253(26)00109-3. Online ahead of print.

Helpful Links

• Related Info

Study record dates

Study Major Dates

• Study Start (Actual): June 14, 2026
• Primary Completion (Estimated): June 1, 2037
• Study Completion (Estimated): June 1, 2037

Study Registration Dates

• First Submitted: June 16, 2026
• First Submitted That Met QC Criteria: June 20, 2026
• First Posted (Actual): June 25, 2026

Study Record Updates

• Last Update Posted (Actual): June 25, 2026
• Last Update Submitted That Met QC Criteria: June 20, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: active surveillance; organ preservation; adjuvant chemoradiotherapy; early rectal cancer; local excision
• Additional Relevant MeSH Terms: Neoplasms by Site; Neoplasms; Intestinal Diseases; Gastrointestinal Neoplasms; Digestive System Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Colorectal Neoplasms; Intestinal Neoplasms; Rectal Diseases; Rectal Neoplasms; Health Services Administration; Therapeutics; Drug Therapy; Quality of Health Care; Radiotherapy; Outcome Assessment, Health Care; Outcome and Process Assessment, Health Care; Combined Modality Therapy; Chemoradiotherapy; Watchful Waiting; Chemoradiotherapy, Adjuvant
• Other Study ID Numbers: KB/247/2026; 101156165 (Other Grant/Funding Number: Horizon Europe)

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No